Memory formation: a new three-phase model.

A new three-phase pharmacological model of memory formation is proposed: (i) a short-term memory phase lasting 10 min, inhibited by lithium chloride (LiCl) and potassium chloride (KCl), but not by ouabain; (ii) a labile, sodium pump-dependent phase occurring after 10 min, inhibited by ouabain but not by cycloheximide (CXM); and (iii) a permanent, protein synthesis-dependent phase occurring after 30 min and inhibited by CXM. Diphenylhydantoin (DPH), which stimulates Na(+)-K(+)-ATPase activity, overcomes ouabain- and CXM-induced amnesia but not LiCl- or KCl-induced amnesia.